Sen. Bob Menendez (D-N.J.) flatly rejected media reports Friday suggesting that he’s blocking one of President Barack Obama’s appellate court nominees because she’s in a relationship with a federal prosecutor who investigated the senator for corruption during his 2006 campaign.

“It is incredibly disappointing and unfortunate that my real concerns over the suitability of Judge Shwartz to serve a lifetime appointment as circuit court judge have been spun as some petty political vendetta by some of her supporters,” Menendez said in a statement to POLITICO.

“I did not believe it was appropriate, nor was it my intention, to debate Judge Shwartz’s qualifications to serve on the circuit court through the press, but the suppositions and suggestions assigned to my position are false and my concerns are substantive.”

Both The New York Times and The (Newark) Star-Ledger reported in front-page stories Friday that Menendez has stalled the nomination of Patty Shwartz for the U.S. Court of Appeals for the Third Circuit, marking the first time one of Obama’s judicial picks had been blocked by a member of his own party.

Both papers reported that Shwartz’s companion of more than two decades is James Nobile, the head of the public corruption unit for New Jersey’s U.S. Attorney’s Office. Nobile, the Times reported has served both Democratic and Republican U.S. Attorneys, including Chris Christie, now the state’s popular GOP governor.

That unit launched a 2006 probe into Menendez’s ties to a nonprofit that rented space from him for nearly a decade, an investigation that Republicans used to bludgeon Menendez and that he suspected was politically driven. The case was closed last October with no charges ever filed.

“[T]he connection has led lawyers and judges in the state to speculate that Mr. Menendez is acting out of resentment, rather than any concern about Judge Shwartz’s qualifications,” The Times wrote.

In his statement, Menendez said it was “completely untrue” that he would hold up a nominee because of an association with the U.S. Attorney’s Office, though he didn’t specifically mention Nobile. The senator pointed out that he’s backed several nominees who worked in that office, including Judge Michael Chagares, whom President George W. Bush nominated for the Third Circuit.

Menendez said he had supported the candidate the White House initially considered for the seat to which Shwartz was nominated, but that he didn’t know why that candidate was not ultimately picked. Menendez said he learned of Shwartz’s possible nomination to the Third Circuit only upon interviewing her for an opening on the U.S. District Court for New Jersey.

“I proceeded to ask her substantive legal questions and was not fully satisfied with her responses,” Menendez said. “In my opinion, Judge Shwartz did not adequately demonstrate the breadth of knowledge of constitutional law and pivotal Supreme Court decisions such as Citizens United that we should expect from a United States Circuit Court judge.”

“In the interview with Judge Shwartz, in my opinion, she misapplied the application of strict scrutiny versus rational basis review to the questions at hand,” Menendez added. “She did not express substantive knowledge as to the scope of the rights of corporations under the Constitution or jurisprudence on the constitutional limits of Executive Branch powers.

As a courtesy, senators are given an opportunity to block a judicial nomination from their home state, a process known as “blue-slipping” — named for the color of paper used to indicate whether they back the nominee. To kill the court pick, the senator need only fail to return the blue slip to the Judiciary Committee. No explanation is required.

Both of New Jersey’s Democratic senators interviewed Shwartz last year and voiced no objections. But while Sen. Frank Lautenberg has returned his blue slip, Menendez has not, said Erica Chabot, a spokeswoman for Judiciary Committee Chairman Patrick Leahy (D-Vt.).

“As is the policy with respect to blue slips under Chairman Leahy, the committee does not proceed to schedule a hearing on a pending judicial nomination until blue slips from both home state senators are received,” Chabot said Friday.

White House officials wouldn’t say whether Obama is disappointed by Menendez, even as the president took unilateral action this week and used controversial recess appointments to seat consumer watchdog Richard Cordray and three National Labor Relations Board who had been filibustered by Senate Republicans.

“Judge Patty Shwartz is an exceptionally well-qualified nominee and we are hopeful she will be confirmed in short order to fill this important seat on the 3rd Circuit,” said White House spokesman Eric Schultz.

In nominating her last October, Obama said in a statement: “Judge Shwartz has a long and impressive record of service and a history of handing down fair and judicious decisions.” A spokesman for Lautenberg said the senator thinks Shwartz is “an excellent choice.”

Shwartz, a former assistant U.S. attorney in New Jersey, has served as a federal magistrate judge in Newark since 2003. The Third Circuit court to which she nominated has jurisdiction over New Jersey, Pennsylvania and Delaware.

Menendez, an attorney and a former congressman, served as the chairman of the Democratic Senatorial Campaign Committee in the 2010 cycle. He’s up for reelection this year.